The invention relates to a spinning machine having a plurality of drafting units which each contain several top rollers and bottom rollers, the bottom rollers being constructed as roller sections which are disposed individually and are connected to a drive by means of driving elements which contain shiftable couplings.
Spinning machines having drafting units of the initially mentioned type are known on the basis of JP-A 59-15519, JP-A 62-162029 and DE-A 15 10 705. In the known constructions, the bottom rollers consist of a roller body which is pressed onto a shaft section. The shaft section is horizontally carried by means of roller bearings in holding devices of the machine frame. The moving area of the sliver, in which the top rollers are pressed against the bottom rollers, is therefore situated at a relative large distance from the roller bearings.
An object of the invention is to develop a spinning machine of the initially mentioned type in such a manner that a construction that is as compact as possible and favorable bearing loads are obtained.
This object is achieved according to preferred embodiments of the invention in that the bottom rollers are hollow cylinders which are disposed on stationary shafts.
By means of this development, it is possible to dispose the bottom rollers such that the deflections caused by loads do not result in an increased loading of the roller bearings. In addition, a very compact construction is achieved.
In an advantageous further development of preferred embodiments of the invention, it is provided that the hollow cylinders are each carried by means of roller bearings which are arranged at least approximately symmetrically with respect to the moving area of a sliver. In this case, it is important that the roller bearings are arranged on both sides of this running area of the sliver, so that no tiltings occur in the area of the bearings.
A particularly simple construction is obtained according to preferred embodiments of the invention if the hollow cylinders are, in each case, disposed on shaft stubs which are clamped in an overhung manner into a part of the machine frame. The shaft stubs, which may also be called stud bolts, may be pressed or clamped in a simple manner into holding devices without any resulting problems with respect to space. In particular, advantages are also achieved for the mounting and the dismounting because the holding device can be detached and fastened again without the risk that, the bearings are subjected to an additional load as a result of an excessive stress.
In a further development of preferred embodiments of the invention, it is provided that the hollow cylinders are designed as the outer bearing ring for roller bodies. As a result, favorable dimensions may be achieved for the shaft stubs and the bottom rollers which permit high stability and stiffness while the overall dimensions do not become too large. For the same purpose, it is provided in a further development of the invention that the roller bodies run directly on the respective shaft stub.
In a further development of preferred embodiments of the invention, a common actuating element is provided for the couplings of several bottom rollers of a drafting unit. As a result, it is possible to stop the drafting unit in such a manner that an interruption of the sliver in the drafting unit is avoided so that no difficulties arise when the drafting unit is switched on again. For the same purpose, it is advantageous for a braking device to be assigned to the bottom rollers. As a result, it is possible to stop the bottom rollers in a defined manner.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.